1. Field of the Invention
The present invention relates to programmable logic circuits, and in particular to an antifuse-based programmable logic circuit providing a wide fanin functionality.
2. Description of the Related Art
Antifuses are well-known in the art of integrated circuits. An antifuse is a structure which is non-conductive when manufactured, but becomes permanently conductive by applying a predetermined voltage across its terminals. Antifuses are typically used with a programmable logic device (PLD) to selectively interconnect conductive lines. For example, FIG. 1 illustrates a PLD 100 which includes a logic module 101 having twelve input lines, i.e. lines 104.sub.1 -104.sub.6 and lines 105.sub.1 -105.sub.6, and one output line 106. Lines 104.sub.1 -104.sub.6 and lines 105.sub.1 -105.sub.6 are connected to lines 102.sub.1 -102.sub.N and lines 103.sub.1 -103.sub.N, respectively, by programing antifuses 107.
Thus, this configuration limits fanin to the number of input lines (in this example twelve input lines). Hence, user applications requiring wider fanin require multiple passes of logic modules, thereby slowing performance. Therefore, a need arises for a PLD having a wide fanin functionality.